Lte-based wireless communication system for the m-lms band

ABSTRACT

A receiver capable of receiving and a transmitter capable of transmitting LTE (Long-Term Evolution) signals. The receiver is capable of executing firmware to determine position location from a received LTE-like position waveform over signals modulated on a carrier in a positioning frequency band. In one embodiment the positioning signals are transmitted in a positioning band continuously for up to 100 ms, allowing the receiver to integrate the received positioning signals over a period of up to 100 ms. In one such embodiment, the signals can be integrated coherently for up to 60 ms, assuming acceptable stability of the clock in the receiver and further assuming that less than a predetermined amount of Doppler shift has been introduced in the received signal. The number of physical resource blocks (PRB) can be determined to optimize the signal allocation for the available bandwidth.

RELATED APPLICATIONS

This application relates to U.S. Patent Application Ser. No. 62/117,580,filed Feb. 18, 2015, entitled AN LTE-BASED WIRELESS COMMUNICATION SYSTEMFOR THE M-LMS BAND, the content of which is hereby incorporated byreference herein in its entirety.

FIELD

Various embodiments relate to wireless communications, and moreparticularly, to transmitting positioning signals over an M-LMS bandfrom an LTE (Long-Term Evolution) base station.

BACKGROUND

Quickly and accurately estimating the location of things within ageographic area can be very useful. For example, information regardingthe location of people or items can be used to speed up emergencyresponse times, track movement of items and people, and link consumersto nearby businesses. Most approaches rely on a process calledtrilateration. Trilateration uses geometry to estimate the position ofan object using distances traveled by different positioning signals(also referred to as “ranging” signals) that are transmitted from threeor more transmitters to receivers that are co-located with the object tobe located.

Various networks of transmitters have been used to transmit positioningsignals. For example, orbiting satellites in the Global PositioningSatellite (GPS) system transmit positioning signals. Each GPS satellitetransmits a positioning signal on which a coarse/acquisition code ismodulated. The positioning signal is received by a GPS receiver. The GPSreceiver identifies the time the positioning signal was transmitted bythe satellite. The receiver also determines a relative time of arrivalbased on an internal clock in the receiver. Once the transmission timeand the relative reception times of the positioning signal are known,the receiver uses measurements from at least three satellites to solve aset of simultaneous equations to determine the position and relativeclock offset for the receiver.

Unfortunately, GPS signals are very faint, which means that the signalsrequire integration over a very long time for a receiver to acquire aGPS signal and to demodulate enough information from the signal todetermine the range measurements necessary to determine the location ofthe receiver. In many cases, the range measurements are not as accurateas may be desired due to the fact that the signals may take indirectpaths from the GPS satellites to the receiver. Acquiring enoughinformation to compute an estimated range measurement associated with adirect path from each GPS satellite to the receiver may take additionaltime and processing power.

Receiving weak GPS signals in urban environments poses additionalproblems. Weak GPS signals often cannot reach receivers throughbuildings. In addition, in such urban environments, GPS signals are morelikely to take multiple paths by reflecting off buildings. As notedabove, such “multipathing” disrupts a receiver's ability to accuratelyestimate a range measurement between the receiver and the satellite. Oneway to address the challenges of determining the position location of adevice in an urban environment is to use terrestrial transmittersystems. Such terrestrial transmitter systems provide stronger signals.Furthermore, terrestrial transmitter systems can include transmitters atdifferent locations within the urban environment that reduce the numberof instances when there is no direct path between the satellite and thereceiver.

Examples of terrestrial transmitter systems that transmit positioningsignals are described in U.S. Pat. No. 8,130,141 (the “'141 patent”). Inat least one embodiment of the '141 patent, each terrestrial transmitteruses a GPS-like channel to transmit a precisely-timed positioningsignal. The receiver computes its location by processing the positioningsignals from three or more terrestrial transmitters, similar to the wayin which the receiver would process GPS positioning signals from threeor more GPS satellites. Since most (if not all) receivers understand howto process GPS signaling, the signals transmitted by such a terrestrialtransmitter system can be used by existing receivers with minimal (orno) modifications to those receivers.

Even though terrestrial transmitter systems provide a more-reliablepositioning service than GPS, such terrestrial transmitter systems mayrequire a substantial amount of additional infrastructure to transmitthe terrestrial positioning signals. Therefore, it would be desirable toreduce the need for such additional terrestrial hardware.

In addition to using terrestrial positioning signals transmitted fromstations dedicated to sending such positioning signals, cellulartelephones are capable of performing ranging measurements, such asobserved time difference of arrival (OTDOA) measurements on cellulartelephone signals, such as LTE (Long-Term Evolution) signals. Suchsignals are transmitted with waveforms organized in resource blocks.Each resource block consists of 7×12 resource elements in the case ofnormal cyclic prefix. In one embodiment in which an extended cyclicprefix is used, a Physical Resource Block (PRB) only has 6 symbols. Aresource element represents the allocation of one symbol in time to oneOFDM (Orthogonal Frequency Division Multiplexing) sub-carrier infrequency. A typical LTE waveform is transmitted at a frequency that isdifferent from the frequency of dedicated terrestrial positioningsystems, such as systems that conform to the well-known M-LMS industrystandard. Typical LTE waveforms used to communicate positioninginformation comprise 50 resource blocks transmitted over a period of 6ms. Accordingly, when determining the time difference of arrival of suchLTE signals, the received signal is integrated over a period of no morethan 6 ms. Restricting the positioning signals to 6 ms reduces theamount of bandwidth consumed by the positioning signals.

While it is advantageous to use LTE signals for ranging due to theubiquitous nature of the LTE, there are several deficiencies with usingthe LTE signals for ranging. For one, it would be advantageous to beable to integrate over longer times. In addition, it would beadvantageous to have waveforms that conform with a format optimized forposition location rather than to a cellular telephone format, such asthe signals that are transmitted by M-LMS (Multilateration and LocationMonitoring Service) systems.

SUMMARY

Various embodiments described in this disclosure relate generally tomethods, systems, means, and machine-readable media for reducing thenumber of additional terrestrial transmitters required to provide areliable “position location” system (i.e., a “positioning” system thataids in determining the position of a receiver). Such methods, systems,means and machine-readable media may use pre-existing cellular telephoneinfrastructure to supplement terrestrial transmitter systems fordetermining the location of a receiver.

Certain embodiments include a receiver capable of receiving LTE(Long-Term Evolution) signals and capable of executing instructionsembodied in firmware, software or the like, in order to determineposition location information from a received LTE-like positionwaveform. In one embodiment, positioning signals are transmittedcontinuously for what is referred to as a “positioning period” of up to100 ms, allowing the receiver to integrate the received positioningsignals over that positioning period. The positioning signals can beintegrated coherently for up to 60 ms, assuming acceptable stability ofa clock in the receiver, and further assuming that less than apredetermined amount of Doppler shift has been introduced in thereceived signal. For integration over a period greater thanapproximately 60 ms, the integration can be done non-coherently.

Instructions may be executed by a physical layer controller thatcontrols a radio frequency section (RF) of the receiver. Under thecontrol of the firmware, the physical layer controller (i.e., PHYcontroller) instructs the RF section of the receiver to tune to a centerfrequency and indicates the number of PRB (physical resource blocks) tobe used to generate the waveform. The center frequency is outside theLTE band. In addition, the number of PRBs (each having a bandwidth of180 kHz (i.e., 12 sub-carriers multiplied by 15 kHz each) determines thebandwidth of the waveform. In one embodiment, the frequency to which theRF section tunes is in the M-LMS (Multilateration and LocationMonitoring Service) frequency band. The PHY controller also instructsthe RF section to receive the signal in accordance with an LTE-likeformat that has 40 PRBs for a bandwidth of approximately 7.2 MHz. Theresulting signal is then pulse shaped to constrain the signal to thedesired frequency mask. In one embodiment, the result of the pulseshaping is a signal having a bandwidth of 8 MHz. Alternatively, theLTE-like format has 37 PRBs for a bandwidth of 6.66 MHz which is pulseshaped to fit within a 7.5 MHz mask.

In one embodiment, an LTE-like format can have other numbers of PRBs,where a PRB is defined according to the LTE standard. Each such PRBincludes 12 subcarriers, and each sub-carrier has a bandwidth ofapproximately 15 kHz and extends for a period of 1 ms (i.e., theduration of an LTE subframe).

A receiver may receive a waveform that includes a number of continuoussubframes. The PHY controller may instruct the RF section to receive thenumber of subframes that are included in the waveform. In oneembodiment, the waveform includes up to 100 or more subframes. Inanother embodiment, the waveform includes 60 subframes and the receiverperforms coherent integration on the received signals. In yet anotherembodiment, the waveform includes 200 subframes. In yet anotherembodiment, the waveform includes n subframes, where n is greater than astandard number of subframes.

The receiver may also decover the signal, including the PRS (positionreference signal) samples, integrating them across the predeterminednumber of subframes to maximize the strength of the decoveredpositioning signal.

By using firmware to control the PHY controller, the RF section can becontrolled in a way that uses LTE standard PRBs to allow the RF sectionto generate a new LTE format that is particularly well-suited forgenerating positioning signals, such as M-LMS signals. Thus, thereceiver may operate in accordance with the general operation of an LTEreceiver, with the only change being to the firmware to instruct the RFsection to generate a new waveform having a non-LTE standard number ofPRBs at a non-LTE center frequency for a duration that is greater thanthe LTE waveform.

A transmitter may be capable of transmitting LTE signals and capable ofexecuting instructions to form LTE-like positioning signals having aduration of greater than 6 ms transmitted at a carrier frequency withina terrestrial positioning system spectrum, such as the spectrum used byM-LMS. In one embodiment, the instructions control the operation of adigital signal processor (DSP) within the physical layer of thetransmitter.

In another embodiment, the signals that are transmitted during thepositioning period use a different type of modulation that is optimizedfor the positioning application—e.g., based on direct sequence spreadspectrum (DSSS), such as employed in systems currently deployed in theM-LMS band, where LTE-based signals are transmitted at the remainingtimes.

Details of embodiments are set forth in the drawings and the descriptionbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a positioning system.

FIG. 2 depicts a simplified block diagram of an LTE transmitter.

FIG. 3 illustrates of one embodiment of the structure of a waveform.

FIG. 4 shows additional details regarding the structure of an LTEwaveform.

FIG. 5 depicts a simplified functional block diagram of the PHY layer ofa transmitter.

FIG. 6 illustrates an LTE waveform where there are 40 PRBs in each slot.

FIG. 7 depicts a simplified block diagram of a receiver that is capableof receiving positioning signals in a positioning frequency band.

FIG. 8 depicts a simplified functional block diagram of the PHY layer ofthe receiver.

Like reference numbers and designations in the drawings indicate likeelements.

DETAILED DESCRIPTION

FIG. 1 illustrates a positioning system 100. The positioning system 100includes any number of receivers, including a receiver 120 that receivesignals from transmitters 110, satellites 150, and/or other system nodes160 via corresponding transmitted communication signals 113, 153 and163. The receiver 120 may also receive information from a backend system130 through the transmitters 110 and from other receivers. For the sakeof simplicity, the connections between the backend system 130 and eachof the transmitters 110 is not shown.

The transmitters 110 may be configured to transmit signals 113 that arereceived by the receiver 120. The transmitters 110 communicate with thebackend 130 via the transmitted communication signals 133. In someembodiments, the transmitters 110 transmit the signals 113 using one ormore common multiplexing schemes, such as time multiplexing usingdifferent time slots, code division multiplexing using differentpseudorandom sequences, or frequency division multiplexing usingdifferent frequencies. Each of the signals 113 from each of thetransmitters 110 may carry different information that, once extracted bythe receiver 120 or the backend 130, may identify the following: (1) thetransmitter that transmitted the signal; (2) the latitude, longitude andaltitude (LLA) of that transmitter; (3) pressure, temperature and otheratmospheric conditions at or near that transmitter; (4) ranginginformation that is used to measure a distance to that transmitter; and(5) other information. In one embodiment, at least one of thetransmitters 110 is an LTE transmitter capable of sending signals inaccordance with the LTE (Long Term Evolution) standard.

The receiver 120 may include a location computation engine (not shown)to determine positioning information based on the signals 113, 153,and/or 163 received from the transmitters 110, the satellites 150,and/or the nodes 160. The receiver 120 may include a signal processingcomponent (not shown) that: (1) demodulates the received signals 113,153, and/or 163; (2) estimates positioning information like travel timeof the received signals 113, 153, and/or 163; and (3) uses thepositioning information to estimate the position of the receiver 120.

The backend 130 communicates with various other systems, such as thetransmitters 110, the receivers 120, and the other networks 160. Thebackend system 130 may include one or more processor(s), data source(s),and other components (not shown).

One of ordinary skill in the art will appreciate that methods describedherein may be carried out using processors at any or all of thetransmitters 110, the receivers 120, the backend 130, and othercomponents of the system 100.

FIG. 2 is a simplified block diagram of an LTE transmitter 200. An upperprotocol layer module 202 determines the content that is to betransmitted based on information received from another source, such asfrom a backend system 130 (see FIG. 1) or from a network, such as theinternet or a telecommunications network. In one embodiment, the contentto be transmitted is positioning information generated locally (i.e.,either in a physical layer controller (PHY controller) 204 or upperprotocol layers 202 of the receiver 200. Alternatively, the positioninginformation can be generated at a remote location and provided to thetransmitter 200.

In one embodiment in which the information to be transmitted isgenerated or received by the upper protocol layer 202, the informationis provided by the upper protocol layer 202 to the PHY controller 204.The PHY controller 204 determines how much bandwidth is needed totransmit the information. A set of LTE parameters are provided by thePHY controller 204 to the physical layer (PHY layer) 206. In response tothe LTE parameters provided to the PHY layer 206 by the PHY controller204, the PHY layer will modulate the information onto an LTE waveformand couple the LTE waveform to a transmission antenna 208. The currentLTE standard defines positioning reference signals (PRS) that aretransmitted in band (i.e., at the same frequency as the voiceinformation). Accordingly, the LTE standard places a limit on theduration of the PRS signal. In one embodiment, the PRS signals aretransmitted in a positioning frequency band that is distinct from theband used to communicate other information (e.g., voice and othernon-position location related data).

FIG. 3 illustrates the structure of an LTE waveform 300. An LTE waveformis organized as frames 301. Each of the frames 301 is ten milliseconds(ms) long, and comprises ten subframes 303. Each of the subframes 303 isone ms long, and comprises two slots 305 of 0.5 ms each. While a frameis ten ms long, the LTE standard limits PRS signals to a maximum of 6subframes (i.e., 6 ms). Positioning signals that conform to thisstructure are “covered” or “spread” with a pseudo-random number (PRN)code sequence based on a “gold code” sequence.

FIG. 4 shows additional details regarding the structure of an LTEwaveform 300. Each of the slots 305 can be used to transmit a number ofphysical resource blocks (PRBs) 401. Each PRB 401 has a duration of 7symbols in time and is 12 subcarriers wide in frequency (i.e., 7×12resource elements). Each subcarrier is 15 kHz wide. A resource element403 represents the allocation of one symbol in time to one subcarrier infrequency. Accordingly, each PRB 401 comprises 84 resource elements 403.A typical LTE waveform used for cellular telephone communications has 50PRBs centered at frequencies allocated by the Federal CommunicationsCommission (FCC).

When the PHY controller 204 instructs the PHY layer 206 to transmitinformation, the parameters that the PHY controller 204 provides the PHYlayer 206 include: (1) the center frequency at which the LTE waveform isto be transmitted (i.e., the positioning frequency band carrierfrequency); (2) the number of resource blocks that will be used in thewaveform and (3) the number of subframes to be continuously transmitted.

FIG. 5 is a simplified functional block diagram of the PHY layer 206 inone embodiment. The number of PRBs and subframes to be used are providedto the PHY layer 206 by the PHY controller 204 (see FIG. 2). For each ofthe slots 305, a Resource Element Grid Generator (REGG) 502 generates aresource element grid 405 based on the information provided by the PHYcontroller 204. In one embodiment, each of the slots 305 includes 40PRBs 401.

In one embodiment, the REGG 502 is a digital signal processor (DSP) thatgenerates a signal having a bandwidth determined by the number of thePRBs 401 to be included in the grid 405. Alternatively, the REGG 502 isan analog signal processor or module comprising discrete componentscapable of generating the grid 405.

The generated grid 405 is coupled to an LTE modulator 504. The LTEmodulator 504 modulates position location content to be transmitted ontothe signals of the generated grid 405. In one embodiment, the content ismodulated using OFDM (Orthogonal Frequency Division Multiplexing)modulation. An output of the LTE modulator 504 is coupled to a pulseshaping filter module 506 that pulse shapes the signal to be transmittedto fit the waveform into a desired mask. The mask is determined based onthe position frequency band requirements provided by the PHY controller204. The position frequency band requirements include the availablebandwidth and the spectral mask to be used. In one embodiment, theserequirements are dictated by an industry standard. In one embodiment inwhich the bandwidth of the positioning signal is 8 MHz, 40 PRBs 401 areused to generate the grid 405. In an alternative embodiment, thepositioning signal bandwidth is 7.5 MHz, in which case 37 PRBs are usedto generate the grid 405. The output from the filter 506 is coupled toan RF signal generator 508. The RF signal generator 508 up-converts thesignal to the position location carrier frequency. In one embodiment,the M-LMS band is used to transmit positioning signals using a waveformthat is similar to the LTE waveform, but having a non-LTE carrierfrequency, a number of PRBs that differ from the LTE waveform, and beingtransmitted with up to 200 or more subframes. It should be noted that asa consequence of the pulse shaping of the filter 506, the output to theRF signal generator 508 will have an 8 MHz bandwidth, even though thegenerated grid is 40×180 kHz=7.2 MHz.

FIG. 6 is an illustration of an LTE waveform generated in one embodimentin which there are 40 PRBs in each slot. In one such embodiment, 100continuous subframes (having 200 slots) are transmitted together. Inanother embodiment, the number of subframes that are transmittedtogether can vary depending upon the conditions under which signals arebeing transmitted. Under conditions that are more challenging for thereceivers, a greater number of subframes can be transmitted. Forexample, when the transmitter is operating in an urban environment, arelatively large number of subframes can be transmitted together. In onesuch embodiment, 200 or more subframes can be transmitted in a verychallenging environment. In a less challenging environment, 60continuous subframes or less are transmitted together. By continuouslytransmitting more subframes, the receiver can integrate over a longerperiod, increasing the sensitivity of the receiver.

FIG. 7 is a simplified block diagram of a receiver 700 in oneembodiment. Signals transmitted from an LTE transmitter 200 are receivedin an antenna 702. The output from the antenna 702 is coupled to a PHYlayer 704. The PHY layer 704 receives control signals from a PHYcontroller 706. The control signals indicate the structure of thewaveform to be received, including the frequency of the carrier, thenumber of subframes 303 over which the received signal will beintegrated, and the number of PRBs 401 to be received. As noted above inrelation to one embodiment, the signals are received in the M-LMS band.Alternatively, the signals can be received at other frequenciesappropriate for transmission and reception of positioning signals. Forsignals that are received with 200 or more subframes, the receiver canintegrate the received signal over the entire period of 200 or moremilliseconds. In one such embodiment in which the received signal has abandwidth of approximately 8 MHz, the PHY controller 706 instructs thePHY layer 704 that there are 40 PRBs in each slot. Alternatively, thereceived signal may have a bandwidth of 7.5 MHz, in which case, the PHYcontroller 706 will instruct the PHY layer 704 that there are 37 PRBs inthe received signal. It will be understood by those skilled in the artthat the particular number of PRBs to be received may depend upon thenumber of PRBs in the transmitted signals. The number of PRBs, in turn,depends upon the bandwidth of the signal to be transmitted and thefilter used within the transmitter to pulse shape the signal prior toup-converting the signal to the carrier frequency.

FIG. 8 is an exemplary simplified block diagram of a PHY layer 704. Thereceived over-the-air (OTA) signals are coupled from the antenna 702(see FIG. 7) to a receiver down converter 801 within the PHY layer 704.The output of the down converter 801 is coupled to a searcher 803. Thesearcher 803 also receives signals from the PHY controller 706. Thesignals from the PHY controller 706 indicate the number of subframesthat have been continuously transmitted and the number of PRBs in eachslot of each subframe. The searcher 803 uses the number of PRBs to setthe parameter for a PRS. In one embodiment, the PRS includes a gold codethat is OFDM encoded into the PRBs of the received signal. Finding thegold code provides a means to determine the relative distance (i.e.,range) from the transmitter to the receiver.

In addition, the searcher 803 uses the number of subframes to determinehow long to integrate the signal received from the down converter 801.By receiving a signal that has a relatively large number of continuouslytransmitted PRBs, the integration period of the searcher can berelatively long. Increasing the length of the integration periodimproves the sensitivity of the receiver. The output of the searcher 803is a ranging output 805 that can be used to determine the relativedistance between the transmitter and the receiver.

Examples of Other Features in Some Embodiments

Functionality and operation disclosed herein may be embodied as one ormore methods implemented, in whole or in part, by machine(s)—e.g.,processor(s), computers, or other suitable means known in the art—at oneor more locations, which enhances the functionality of those machines,as well as computing devices that incorporate those machines.Non-transitory machine-readable media embodying program instructionsadapted to be executed to implement the method(s) are also contemplated.Execution of the program instructions by one or more processors causethe processors to carry out the method(s). Systems (e.g., apparatuses orcomponents thereof) operable to implement the method(s) are alsocontemplated.

It is noted that method steps described herein may be order independent,and can therefore be performed in an order different from thatdescribed. It is also noted that different method steps described hereincan be combined to form any number of methods, as would be understood byone of skill in the art. It is further noted that any two or more stepsdescribed herein may be performed at the same time. Any method step orfeature disclosed herein may be expressly restricted from a claim forvarious reasons like achieving reduced manufacturing costs, lower powerconsumption, and increased processing efficiency.

By way of example, not by way of limitation, method(s), system(s) orother means may perform the following or be operable perform thefollowing: generating a grid of resource elements, the resource elementswithin the grid being grouped into physical resource blocks (PRBs);organizing the PRBs in slots, each slot having a number of the PRBs; andtransmitting a plurality of the slots in a continuous transmission at afrequency within a frequency band allocated for determining position.

In different embodiments, the number of PRBs is 40 or 37. In at leastone embodiment, the slot is 0.5 milliseconds in duration. In at leastone embodiment, each PRB comprises 7×12 resource elements. In differentembodiments, slots are transmitted in at least 60 consecutive subframes,at least 100 consecutive subframes, or at least 200 consecutivesubframes.

In at least one embodiment, each resource element represents anallocation of one symbol in time to one OFDM (Orthogonal FrequencyDivision Multiplexing) sub-carrier in frequency. In at least oneembodiment, each resource element represents an allocation of one symbolin time to one LTE OFDM (Orthogonal Frequency Division Multiplexing)sub-carrier in frequency.

In at least one embodiment, the frequency band allocated fortransmitting positioning signals is an M-LMS (Multilateration andLocation Monitoring Service) band.

Method(s), system(s) or other means may further or alternatively performthe following or be operable to perform the following: transmitting aLong Term Evolution (LTE) signal over another frequency allocated by theFederal Communications Commission (FCC) for use by cellular telephones.

By way of example, not by way of limitation, method(s), system(s) orother means may perform the following or be operable perform thefollowing: generating a grid of resource elements, the resource elementswithin the grid being grouped into physical resource blocks (PRBs);receiving an Orthogonal Frequency Division Multiplexing (OFDM) modulatedpositioning signal on a frequency for transmitting positioning signals;and searching for positioning information within the receivedpositioning signal using the parameters of the generated grid ofresource elements as search parameters, where the resource elements usedfor positioning information are contiguous.

In different embodiments, the grid of resource elements includes 40 or37 PRBs that are grouped together in a slot. In at least one embodiment,the slot is 0.5 milliseconds in duration. In at least one embodiment,each PRB comprises 7×12 resource elements.

In at least one embodiment, each resource element represents theallocation of one symbol in time to one OFDM sub-carrier in frequency.In at least one embodiment, each resource element represents anallocation of one symbol in time to one LTE OFDM (Orthogonal FrequencyDivision Multiplexing) sub-carrier in frequency.

In at least one embodiment, each resource element represents theallocation of one symbol in time to one OFDM sub-carrier in frequency.

In different embodiments, searching for position information includesintegrating the received signal over at least 60 consecutive subframes,at least 100 consecutive subframes, or at least 200 consecutivesubframes.

In at least one embodiment, the frequency band is an M-LMS(Multilateration and Location Monitoring Service) band.

By way of example, one or more systems may comprise hardware modulesthat perform the methods or particular steps of the methods disclosedherein.

In accordance with certain embodiments, a transmitter for transmittingpositioning signals includes: a resource element grid generator (REGG)having first and second inputs and an output, the first input coupled toreceive a signal indicating a number of physical resource blocks (PRBs)to be included in a generated grid of resource elements, and the secondinput coupled to receive a signal indicating a number of subframes to beconsecutively transmitted by the transmitter; a modulator having a firstinput and an output, wherein the first input is coupled to the output ofthe REGG to receive a signal having a number of PRBs together in a slotand the signal having a number of slots to be consecutively transmittedfrom the transmitter; and a radio frequency (RF) signal generator havinga first input coupled to the output of the modulator to receive amodulated waveform from the modulator, the modulated waveform having anumber of consecutive slots to be contiguously transmitted at afrequency within a frequency band for transmitting a positioning signal.

The transmitter may further comprise: a physical layer (PHY) controller,the PHY controller having a first output coupled to the first input ofthe REGG to provide the signal indicating the number of physicalresource blocks (PRBs) to be included in the generated grid of resourceelements, the PHY controller having a second output coupled to thesecond input of the REGG to provide the signal indicating the number ofsubframes to be consecutively transmitted by the transmitter.

In at least one embodiment, the modulator has a second input coupled tothe PHY controller to receive position location content to be modulatedon the signal received from resource element grid generator.

In at least one embodiment, the RF signal generator has second input toreceive information regarding a carrier frequency to be used fortransmitting the positioning signals.

In different embodiments, the received signal indicating the number ofPRBs to be included in the generated grid of resource elements indicatesthat 40 or 37 PRBs are to be included in the generated grid of resourceelements. In at least one embodiment, each PRB comprises 7×12 resourceelements.

In at least one embodiment, each resource element represents theallocation of one symbol in time to one OFDM sub-carrier in frequency.In at least one embodiment, each resource element represents theallocation of one symbol in time to one OFDM sub-carrier in frequency.

In different embodiments, the received signal indicating the number ofsubframes to be consecutively transmitted by the transmitter indicatesthat the number of subframes to be consecutively transmitted is 60, 100or 200.

In at least one embodiment, the frequency band allocated by the FCC fortransmitting positioning signals is an M-LMS (Multilateration andLocation Monitoring Service) band.

In accordance with certain embodiments, a receiver of positioningsignals includes: a down converter having a first input to receive anOrthogonal Frequency Division Multiplexing (OFDM) modulated positioningsignal, the down converter having a second input to receive informationregarding a carrier frequency of the received positioning signal; and asearcher having a first input coupled to receive a signal indicating anumber of physical resource blocks (PRBs) to be included in a search forposition information within the received positioning signal, and havinga second input coupled to receive a signal indicating a number ofsubframes over which the searcher is to integrate the receivedpositioning signal in performing the search for positioning information.

In different embodiments, the received positioning signal comprises aplurality of consecutively transmitted slots, each slot of the receivedpositioning signal having 40 or 37 PRBs. In different embodiments, thesignal indicating the number of PRBs indicates that there are 40 or 37PRBs in each slot of the received positioning signal.

In different embodiments, the received positioning signal comprises 60,100 or 200 subframes. In different embodiments, the signal indicatingthe number of subframes indicates that the search is to integrate across60, 100 or 200 subframes of the received signal. In at least oneembodiment, each PRB comprises 7×12 resource elements.

In at least one embodiment, each resource element represents theallocation of one symbol in time to one OFDM sub-carrier in frequency.In at least one embodiment, each resource element represents theallocation of one symbol in time to one OFDM sub-carrier in frequency.

In at least one embodiment, each module includes one or more inputs toreceive information used to perform what it is operable to do, andfurther includes one or more outputs to send information to othermodules.

A “receiver” may be in the form of a computing device (e.g., a mobilephone, a tablet, a PDA, a laptop, a digital camera, a tracking tag). Areceiver may also take the form of any component of the computer,including a processor. Processing by the receiver can also occur at aserver.

The illustrative methods described herein may be implemented, performed,or otherwise controlled by suitable hardware known or later-developed byone of skill in the art, or by firmware or software executed byprocessor(s), or any combination of hardware, software and firmware.Software may be downloadable and non-downloadable at a particularsystem. Such software, once loaded on a machine, changes the operationof that machine.

Systems on which methods described herein are performed may include oneor more means that implement those methods. For example, such means mayinclude processor(s) or other hardware that, when executing instructions(e.g., embodied in software or firmware), perform any method stepdisclosed herein. A processor may include, or be included within, acomputer or computing device, a controller, an integrated circuit, a“chip”, a system on a chip, a server, other programmable logic devices,other circuitry, or any combination thereof.

“Memory” may be accessible by a machine (e.g., a processor), such thatthe machine can read/write information from/to the memory. Memory may beintegral with or separate from the machine. Memory may include anon-transitory machine-readable medium having machine-readable programcode (e.g., instructions) embodied therein that is adapted to beexecuted to implement any or all of the methods and method stepsdisclosed herein.

Memory may include any available storage media, including removable,non-removable, volatile, and non-volatile media—e.g., integrated circuitmedia, magnetic storage media, optical storage media, or any othercomputer data storage media. As used herein, machine-readable mediaincludes all forms of machine-readable media except to the extent thatsuch media is deemed to be non-statutory (e.g., transitory propagatingsignals).

All of the information disclosed herein may be represented by data, andthat data may be transmitted over any communication pathway using anyprotocol, stored on data source(s), and processed by a processor.Transmission of data may be carried out using a variety of wires,cables, radio signals and infrared light beams, and an even greatervariety of connectors, plugs and protocols even if not shown orexplicitly described. Systems may exchange information with each otherusing any communication technology. Data, instructions, commands,information, signals, bits, symbols, and chips and the like may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, or optical fields or particles.

Features in system figures that are illustrated as rectangles may referto hardware, firmware or software. It is noted that lines linking twosuch features may be illustrative of data transfer between thosefeatures. Such transfer may occur directly between those features orthrough intermediate features. Where no line connects two features,transfer of data between those features is contemplated unless otherwisestated.

When two things (e.g., modules, circuit elements, etc.) are “coupled to”each other, those two things may be directly connected together, or maybe separated by one or more intervening things. Thus, no directconnection is required between the two things Where an output and aninput are coupled to each other, data and/or signaling sent from theoutput is received by the input even if the data passes through one ormore intermediate things

The words comprise, comprising, include, including and the like are tobe construed in an inclusive sense (i.e., not limited to) as opposed toan exclusive sense (i.e., consisting only of). Words using the singularor plural number also include the plural or singular number,respectively. The word or and the word and, as used in the DetailedDescription, cover any of the items and all of the items in a list. Thewords some, any and at least one refer to one or more. The term may isused herein to indicate an example, not a requirement—e.g., a thing thatmay perform an operation or may have a characteristic need not performthat operation or have that characteristic in each embodiment, but thatthing performs that operation or has that characteristic in at least oneembodiment.

It is noted that the term “GPS” may refer to any Global NavigationSatellite Systems (GNSS), such as GLONASS, Galileo, and Compass/Beidou,and vice versa.

1. A method for transmitting positioning signals, the method comprising:generating a grid of resource elements, the resource elements within thegrid being grouped into physical resource blocks (PRBs); organizing thePRBs in slots, each slot having a number of the PRBs; and transmitting asignal used for positioning in multiple contiguous slots in a continuoustransmission at a frequency within a frequency band allocated fordetermining position.
 2. The method of claim 1, wherein the number ofPRBs is 37 or 40, and each PRB comprises 7×12 resource elements.
 3. Themethod of claim 1, wherein each resource element represents anallocation of one symbol in time to one LTE OFDM (Orthogonal FrequencyDivision Multiplexing) sub-carrier in frequency.
 4. The method of claim1, wherein transmitting the slots includes transmitting the slots in atleast 60 consecutive subframes.
 5. The method of claim 1, wherein thefrequency band allocated for transmitting positioning signals is anM-LMS (Multilateration and Location Monitoring Service) band.
 6. Themethod of claim 1, further comprising: transmitting a Long TermEvolution (LTE) signal over another frequency allocated by the FederalCommunications Commission (FCC) for use by cellular telephones.
 7. Amethod for receiving positioning signals, the method comprising:generating a grid of resource elements, the resource elements within thegrid being grouped into physical resource blocks (PRBs); receiving anOrthogonal Frequency Division Multiplexing (OFDM) modulated positioningsignal on a frequency for transmitting positioning signals; andsearching for positioning information within the received positioningsignal using the parameters of the generated grid of resource elementsas search parameters, where multiple resource elements used forpositioning information are contiguous.
 8. The method of claim 7,wherein the grid of resource elements includes 37 or 40 PRBs that aregrouped together in a slot, and each PRB comprises 7×12 resourceelements.
 9. The method of claim 7, wherein each resource elementrepresents an allocation of one symbol in time to one LTE OFDM(Orthogonal Frequency Division Multiplexing) sub-carrier in frequency.10. The method of claim 7, wherein searching for position informationincludes integrating the received signal over at least 60 consecutivesubframes.
 11. The method of claim 7, wherein the frequency band is anM-LMS (Multilateration and Location Monitoring Service) band.
 12. Apositioning system comprising: a transmitter that includes: a resourceelement grid generator (REGG) having first and second inputs and anoutput, the first input coupled to receive a signal indicating a numberof physical resource blocks (PRBs) to be included in a generated grid ofresource elements, and the second input coupled to receive a signalindicating a number of subframes to be consecutively transmitted by thetransmitter; a modulator having a first input and an output, wherein thefirst input is coupled to the output of the REGG to receive a signalhaving a number of PRBs together in a slot and the signal having anumber of slots to be consecutively transmitted from the transmitter;and a radio frequency (RF) signal generator having a first input coupledto the output of the modulator to receive a modulated waveform from themodulator, the modulated waveform having a number of consecutive slotsto be contiguously transmitted at a frequency within a frequency bandfor transmitting a positioning signal.
 13. The system of claim 12,wherein the transmitter further includes: a physical layer (PHY)controller, the PHY controller having a first output coupled to thefirst input of the REGG to provide the signal indicating the number ofphysical resource blocks (PRBs) to be included in the generated grid ofresource elements, the PHY controller having a second output coupled tothe second input of the REGG to provide the signal indicating the numberof subframes to be consecutively transmitted by the transmitter, whereinthe modulator has a second input coupled to the PHY controller toreceive position location content to be modulated on the signal receivedfrom resource element grid generator.
 14. The system of claim 12,wherein the RF signal generator has second input to receive informationregarding a carrier frequency to be used for transmitting thepositioning signal.
 15. The system of claim 12, wherein the receivedsignal indicating the number of PRBs to be included in the generatedgrid of resource elements indicates that 37 or 40 PRBs are to beincluded in the generated grid of resource elements, and wherein eachPRB comprises 7×12 resource elements.
 16. The system of claim 15,wherein each resource element represents the allocation of one symbol intime to one OFDM sub-carrier in frequency.
 17. The system of claim 12,wherein the received signal indicating the number of subframes to beconsecutively transmitted by the transmitter indicates that the numberof subframes to be consecutively transmitted is
 60. 18. The system ofclaim 12, wherein the frequency band allocated by the FCC fortransmitting the positioning signal is an M-LMS (Multilateration andLocation Monitoring Service) band.
 19. The system of claim 12, thesystem further comprising: a receiver that includes: a down converterhaving a first input to receive an Orthogonal Frequency DivisionMultiplexing (OFDM) modulated positioning signal, the down converterhaving a second input to receive information regarding a carrierfrequency of the received positioning signal; and a searcher having afirst input coupled to receive a signal indicating a number of physicalresource blocks (PRBs) to be included in a search for positioninformation within the received positioning signal, and having a secondinput coupled to receive a signal indicating a number of subframes overwhich the searcher is to integrate the received positioning signal inperforming the search for positioning information.
 20. The receiver ofclaim 19, wherein the received positioning signal comprises a pluralityof consecutively transmitted slots, wherein each slot of the receivedpositioning signal having 37 or 40 PRBs, wherein the signal indicatingthe number of PRBs indicates that there are 37 or 40 PRBs in each slotof the received positioning signal, and wherein each PRB comprises 7×12resource elements.